Project description:We performed STARR-seq with synthetic libraries (synSTARR-seq) in GR18 cell line (derived from U2OS ATTC:HTB-96, stably transfected with an expression construct for GR), upon glucocorticoid (dexamethasone) or vehicle (ethanol) treatment. The synthetic libraries are variants of the glucocorticoid receptor binding sites (GBS). The "GBS half site" library contains 8 consecutive randomized nucleotides within the core binding sites, while the "Cgt/Sgk library" contains 5 consecutive randomized nucleotides on the flank of the GBS.
Project description:Transcription activator-like effector nucleases (TALENs) are programmable nucleases that have entered the clinical stage. Each subunit of the dimer consists of a DNA-binding domain composed of an array of TALE repeats fused to the catalytically active portion of the FokI endonuclease. Upon DNA-binding of both TALEN arms in close proximity, the FokI domains dimerize and induce a staggered-end DNA double strand break. In this present study, we describe the implementation and validation of TALEN-specific CAST-Seq (T-CAST), a pipeline based on CAST-Seq that identifies TALEN-mediated off-target effects, nominates off-target sites with high fidelity, and predicts the TALEN pairing conformation leading to off-target cleavage. We validated T-CAST by assessing off-target effects of two promiscuous TALENs designed to target the CCR5 and TRAC loci. Expression of these TALENs caused high levels of translocations between the target sites and various off-target sites in primary T cells. Introduction of amino acid substitutions to the FokI domains, which render TALENs obligate-heterodimeric (OH-TALEN), mitigated the aforementioned off-target effects without loss of on-target activity. Our findings highlight the significance of T-CAST to assess off-target effects of TALEN designer nucleases and to evaluate mitigation strategies, and advocate the use of obligate-heterodimeric TALEN scaffolds for therapeutic genome editing.
Project description:The submitted dataset contains raw files from 96 synthetic peptide libraries, using either HCD or ETD as fragmentation technique. The synthesized 96 tryptic peptide libraries containing >100,000 unmodified peptides plus their corresponding >100,000 phosphorylated counterparts with precisely known sequences and modification sites. All these libraries were subjected to LC-MS/MS on an Orbitrap mass spectrometer using HCD and ETD fragmentation. The generated mass spectrometric data deposited in this database can be used in numerous ways to develop, evaluate and improve experimental and computational proteomic strategies. Raw MS data files were converted into Mascot generic format files (MGF) using Mascot Distiller (2.4.2.0, www.matrixscience.com). Important parameters included: i) signal to noise ratio of 20 for MS/MS and ii) time domain off (no merging of spectra of the same precursor). The MGF files were searched against human IPI v3.72 including the sequences of all 96 libraries,using the Mascot search engine (2.3.1, 24). Search settings: Decoy search using a randomized version of the human IPI v3.72 including the sequences of all 96 libraries was enabled; monoisotopic peptide mass (considering up to two 13C isotopes); trypsin/P as protease; a maximum of four missed cleavages; peptide charge +2 and +3; peptide tol. +/- 5 ppm; MS/MS tol. +/- 0.02 Da; instrument type ESI-Trap (for HCD data) or ETD-Trap (for ETD data) respectively; variable modifications: oxidation (M), phospho (ST), phospho (Y). The result files were exported to pepXML and Mascot XML with default options provided by Mascot.